Which of the following reactions are exothermic?

 

$$\begin{gathered} 1) C + O2 → CO2 \\ 2) 2Mg + O2 → 2MgO \\ 3) CuSO4 + 5H2O → CuSO4.5H2O \\ 4) All the above \end{gathered}$$

The number of protons in an isotope or an atom gives its atomic number whereas the number of protons and neutrons gives its mass number.

In a concentrated solution there is a large amount of solute.

German Silver is an alloy of copper, nickel and zinc. It is composed of 60% copper, 20% nickel and 20% zinc. Due to its white-silverish appearance it is named as german silver but it contains no silver in it.

The minimum amount of energy required for a particular reactants to convert into products and is called as Activation Energy.

This activation complex is also termed as Transition State because according to Transition State Theory at transition state the existing bonds tend to increase in length and become weaken while, the new forming bonds tend to decrease in length and start becoming stronger.

Hence, the activated complex is in transition between reactants and products.

Law of Octaves states that "If the chemical elements are arranged according to increasing atomic weight, those with similar physical and chemical properties occur after each interval of seven elements." That is every 8th element have the same physical and chemical properties. This was established by the British scientist John Newlands in the year 1865.

We know that each successive IE is greater than the previous one, because each ionization process removes one electron and hence increases the total attractive force on the remaining electrons from the nucleus. Hence, C3+ (g) → C4+ (g) + e- needs more energy.

Many toxic gases along with water vapour are emitted in vocanic eruptions. All such toxic gases include hydrochloric acid, sulfur dioxide, carbon dioxide, hydrogen sulfide and carbon monoxide. Methane is not produced in the volcanic eruptions.

Endothermic reaction is the reaction in which energy is obserbed for the change.